DE 40 38 674 A1 discloses a magnetically operating path and/or position measuring device. This has a conventional permanent magnet and a sensor detecting the magnetic field intensity. The magnet and/or the sensor co-operate with a movable element, so that a relative movement between the sensor and the magnet can be brought about by means of the movable element. In the magnetic circuit there is a rail which is made of material with good magnetic conduction and is arranged obliquely with respect to the relative movement, whereby the magnetic field intensity is influenced in a way corresponding to the relative movement, so that the path and/or the position of the movable element can be determined on the basis of the magnetic field intensity detected by the sensor. Instead of such a rail, an increasing air gap may also be provided between the magnet and the sensor, producing a smaller field intensity at the sensor, dependent nonlinearly on the distance between the magnet and the sensor. A disadvantage of devices of such a design appears to be their low sensitivity, inadequate accuracy and also the effort involved in evaluating the magnetic field intensity for the path and/or position determination.
Furthermore, EP 1 099 929 A1 discloses a path and/or position measuring device comprising a magnet which is formed in such a way that the magnetic field intensity varies along an axis of the magnet. A movable element co-operates with the magnet, whereby a relative movement between the sensor and the magnet substantially in the direction of this axis of the magnet can be brought about. On the basis of the magnetic field intensity detected by the sensor, the path and/or the position of the movable element can in turn be determined. A disadvantage of this path and/or position measuring device appears to be its large and complex mechanical form.